Hydraulic brake system



O ct. 15, 1946.

Y. Z. VON STACKELBERG HYDRAULIC BRAKE SYSTEM Filed NOV. 22; 1944 J Yui*geh Z.von Srackelberg Patented Oct. 15, 1946 HYDRAULIC BRAKE SYSTEM Yurgen Z. von Stackelberg, Baltimore, Md. assignor to The Glenn L. Martin Company, Middle River, Md. a. corporation cf Maryland Application November 22, 1944, Serial N0. 564,594

11 Claims. (GI. 188152) This invention relates 110 a hydraulic braking system,- particularly for aircraft, and its prima object is to provide a hydrauli braking system including an emergency fluid system whereby th blakes may be operated in the event the fiuid pressure pump fails o1 where the normal fluid line conveying fluid 110 the brakes has been ruptured.

It is more or less :onventional in aircraft braking Systems to energize the wheel brakes by utilizing a fluid pressure system comprising a fluid reservoir and pump connected thereto fur forcing fluid under pressure to foot-controlled valves which are attached to the right and left rudder pedals of an aircraft for operation by the pilot, With the Fluid under pressure controllecl thereby communicating With the wheel brakes for applying actuating pressure thereto. It is obvious that the fluid pressure lines leading from the 15001:- controlled brakes on the rudder pedal to the wheel brakes a1e quite vulnerable and thai; if these lines rupture there would be no pressure available for actuating the brakes. Furthermore, this dangerous condition may occur if the pressure pum develops any mechanical difilculty and fai1s to maintain the necessary fiuid pressure in the operating 1ines.

It is usual to carry a compressed air bottle having a manually controlled valve thereon and a separate air circuit to the brakes through shuttle valves located adjacent the brakes whereby if the normal fluid 1ine lacks suffiient pressure 130 operate the brakes, the air bottles may be opened to shift the shuttle va1ves and close off fluid therethrough and to permit air from the compressed supply 120 energize the brakes. Hewever, this type of emergency brake operator has several inherent disadvantages inasmuch as the air bottle permits only a Single operation of the brakes, and more important, after the emergency operaoi0n, the entire hydraulic system is contaminated wioh air and. it is ther1 necessary to disconnect and purge the Whole braking system before normal fluid operation can again be effected. The use of compressed air in the brakes, because there is nocontrol over its application 110 the brakes, locks the aircraft wheels and in mos't cases causes the ti'res to be ruined in arresting the plane; As before stated; the greatest di'sadvantage in such an emrgency air system is that the WhOle system must be bled of the air before repairs can be made and the hydraulic fluid sysgern fails because of the non-operation of the fiid pump, such a minor mechanical falilure requires a major overhaul 0f the system beqause of the air in the systems.

In the present invention, the hydraulic braking system include3 a closed, normal fluid system for the brakes, comprising a fluid reservoir and pump, foot; control valves attached to the rudder pedals for passing fiuid to the wheel brakes, and a pair of four-way valves inserted in the fluid 1ines leading from the foot operated brakes, whereby fluid under pressure is normally passed therethrough to the brakes.. A vent; line is provided from shuttle valves on the brakes back through the tour- Way valves and thence a common discharge line, which is connected to the rservoir. A hydraulic fluid accumulator of any accepted design is placed in the fluid line between the pump and the foot oper2mted valves, with a check valve interposed in ehe fluid 1ine betvveen the pump and the accumulator. With this arrangement, the accumulator is kept under full pressure als all times and acts asa pressure equalizer on the line. Upon failure of the pump, tlr1e check valve operates to prevent escape of fluicl from the accumulator back through the pump, and the pressure is maintained at the brake va1ves by the accumulator.

A slhuttle valve similar to that illustrated in Overbzke Patent N0. 2,300694,dated October 3, 1942 is placed on each brake. The valve forms a fittlng to- Which the normal pressure line and the ve'nt 1ine which also forms the emergency fiuid pressure line, are connected. The four-way valves controlling the normal and emergency conduits are preferably made in a single unit and are manually operated -by eh pi1ot, when the feel cf the pedal valves controlling the regular brake lines indicates there is insuflicient fiuid pressure to operate the brakes. By merely f1ipping a 1ever, the plugs of thefour-way valves shift; the fluid pressum from the control valves, from the normal line, into th emergeney line through the shuttle valves. that When the normal fluid lines are used, the

' emergency lines act as vents therefor and comversely when the emergkency lines am used the normal lines act as a vent, and thisventlng operation and use of shuttle valves positively prevents any hydraulic lockin the system. Furthermorejthere is a great advantage attendant to the use of this type of hydraulic system over or rupture of the normal fluid pressure lines' I1: Will be appa3rent leading from the foot brakes to the wheel brakes.

The attached drawing 15 a diagrammatical layout of a fluid system embodying the principles of this invention, but it will be obvious that these principles can be incorporated in fiuid braking systems of other design. Specifically the normal fiuid circuit extends from the fiuid reservoir R having a vent V thr ough pump P and Check va1ve CV to aceumulator A and through main fluid line l to foot operated valves 5 and 5' which may be attached to the rudder pedals of the aircraft and operated Joy linkages 7 and 'l respectively. As shown, the main fluicl 1ine l is branched. into the casings f brake pedal valves and 5', and these valves ma-y De individually vented through vent 1ines 29, 29 to main retllI-Il 1ine 2T. "Ihe four-way valves I5, I5 receive fluid through lines H, H connected to the foohoperated valves 5 and 5. In the position shown, the plugs of the four-way valves pass fluid to the normal brake operating conduits I9, l9 through shuttle valves 2 l, 2! to the whee1 brake B. Vent lines are provided via the four-way valves through emergency lines 23, 23 through the passas of valves I5, l5' and vent line 27 C011- nected to the top of reservoir R.

If the pump P falls or if the normal fiuid 1ines I9, I9 are shot away the pilot operates lever l'l and. moves it from the normal to emergency 100- sition indicated by the letters N and E 150 rotate the plugs of the four-way valves I5, I5 whereby the fluid circuit permits fiuids from the evergharged accumulator A t0 pass through 1ine I, valves 5 and 5' as in normal peration, and thence t0mrgency lines 2.3, 23' and through the shutt1e valves to the brakes. The normal lines I9, I9 then vent; the shuttle valves and prevent any hydraulic lock from occurring. It is preferable 130 Vent the foot-operated valves 5 and 5 independentl5n and this is sho-wn by lines 29, 29' joined to the main return 1ine 2T.

As be for e indicatecl, the accumulator contains sufilcient fiuid pressure to 0p erate the brakes a number of times, and by reason of the check valve CV the accumulator is constantly Charged and available for instant use. When lines I9, I 9 are shot; away, the fluid escapes therefrom and the system does not become pressure locked.

The mechanism described aflorcls an alternate fluid pressure source that operates the brakes in the same manner and With the same feel, after lever I! has been moved from the normal to the emergency position.

It is to be understood that certain changes, a1- terations, modifications and substitutions can be made without departing from the spirit and scope of the appended claims.

I claim as my invention:

1. A hyclraulic brake system comprising a reservoir, a pump to deliver fluid under pressure from the reservoir to a fiuid line, and a brake a pressure contro1 valve in said fluid 1ine controlling the flow of fluid to said brake, said fluid line extending from said pressure control valve to said brake including a flow control valve connected to receive fluid under pressure from the outlet of said pressure control valve and a shutt1e va1ve on said brake, a pair of fluid lines extending from s ai :1 flow control valve to the inlet ports of said shut tle valves, on o f said lines constituting the normal pressure line am]. the other an emergency pressure lin e said flow control valve adapted to direct fiuid through either the normal or emergency pressure line, the other line afforcling a vent for said shutt1e valve through said flow comtrol valve.

2. A hydraulic brake system comprising a res ervoir, a pump, a pressure control valve, a fluid line and a brake, interconnected to cooperate to deliver fiuid under controlled pressure said brake, an accumulator connectecl to said 1ine between said pump and said. control valve to equalize the pressure in said line, said fiuid line extending from said pressure control valve to said brake including a manually operated flow control va1ve connected to receive fluid under pressure from the out1et of said pressure control valve, a shuttle valve mountecl on said brake, a pair of flu i d lines extending from said flow control valve to the inl et ports of said shuttle valves, said manually operated valve so connected that fluid under pressure may be di1ectecl through one 01 the other of the brake lines to said shuttle valve, the 1ine through Which fluid pressure is not directed. afiords a vent for said shuttle valve through said flow contro1 valve.

3. A hydraulic braking system for vehicles comprising a brake, a reservoir, a pump having the inlet side connected to said reservoir, an energizer-accumulator connected to the line on the outlet side of the pump, a check valve between the inlet to the accumulator and said pump, a pressure control valve in said line controlling the pressure of fiuid through the brake line to the brake, said brake line including a flow control valve, a shuttle va1ve mounted on said brake and a pair of conoluits extending from said flow contro1 valve to the inlet ports of said shuttle valve; said flow control valve connected to said pressure control valve to receive fluid therefrom and direct it through either of said pair o-f lines to said shuttle va1ve, the other line affording a vent for said shuttle valve through said flow contro1 va1ve.

4. A hydraulic braking system for vehicles comprising a fluid circuit including a reservoir, a pump for maintaining the fiuid in the circuit; under pressure, a brake, an accumulator secured so the line on the outlet side of the pump acting as a pressure equalizer, means to prevent flow of fluid frbm said accumulator through said pump, a pressure control va1ve for controlling the flow of fluid to said brake on the vehicle, a normal fiuid pressure line extending from said pressure control valve to said brake, a second pressure line extending from said pressure control valve 1:0 said brake, a manually operable flow control valve meang interposed between said pressure control valve and said brake for directing fiuid under pressure through either the normal line or the. secondary line. V

5. A hydraulic braking system including a plur-a1ity of brakes, a fiuid reservoir, a pump and fiuid pressure lines each having a pressure control va1ve for delivering, fluid under controlled pressures from the pump to each brake, an accumulator interposed in the system between the pump and the pressure control valve to equalize the pressure in the system and a manually operated flow control valve in said system for directing fluid under pressure from each of said pressure c ontrol valves saicl bra-kes through one or the other of separate fluid pressure lines.

6. A hydraulic brake system comprising a reservoir, a pump deliver fluid under pressure f rom the reservoir 130 a fluid line, and a brake, a pressure control val.ve in said fluid line controlling the flow 0f fiuid to said brake, said fluid line extending from said pressure control va1ve to said brake including a flow control valve connec'oed to receive fluid under pressure from the out1et of said pressure control valve and a shuttle valve on said brake, a pair of fluid lines extending from said flow control valve to the in1et ports of said shuttle valves, one Of said lines constitutiug the normal pressure line and ehe other an emergency pressure line, said. flow control valve being a manual1y operable valve 130 selectively direct fiuid through either the normal or emergency pressure line, the other line affording a vent for said shuttle valve through said flow control valve.

7. A hydraulic brake system comprising a reservoir, a. pump, a Dressure control valve, a, fiuid 1ine anal a brake, interconnected to cooperate to deliver fluid under controlled pressure 170 sa id brake, said fluid 1ine extending from said pres sure control va1ve to seid brake including a. flow control valve connectea to receive fiuid under pressure from the outlet of said pressure control valve, a. shutle valve mounted 0n said brake, a pair 0f fiuid liues extending from said flow control valve to the inlet ports of said shuttle valves, said flow control valve so connected that fluid under pressure ma.y be directed through one 01 the other of the brake 1ines tdsaid shutt1e valve, the other 1ine aifording a vent for said shuttle valve through said flow control va1ve.

8. A hydraulic braking system for vehicles comprising a reservoir, a. pump having the inlet side connected to said reservoir, an equalizeraccumulator connected so the line on the outlet side 0f the pump, a, check valve between the inlet to the accumulator and said pump, a pressure control valve in each 1ine controlling tne pressure 0f fiuid through brake lines to brakes, each of said brake 1ines includi ng a, flow control valve, a shuttle va1ve mounted on said brake and a pair of concluics extending from said flow control valve 120 the in1et ports of said shuttle valve, said flow control valve connected 1:0 said pressure control valve to receive fluid therefrom and direct it through either of said pair of 1ines to said shuttle va1ve, the other 1ine aifording a vent for said shuttle valve through said flow control valve.

9. A hYdraulic braking system for vehic1es comprising a reservoir, a pump for maintaining fiuid in the system under pmssure, conduits extending from said pump to deliver fiuid under pressure 1:0 the brakes of said vehicle; pressure COI11ZI'OI valves in said. conduits between said pump and said brake and an accumulator connected to the line between the pressure control va1ves and the pump a. Check valve between said accumulator and said pump, said accumulator acting to equalize the pressure in the system maintained by said pump and act as an emergency source of pressure upon failure of the pump.

10. A hydraulic brake system comprising a reservoir, a pump deliver fluid under pressure from the reservoir to a fluid 1ine, and a brake a pressure contro1 valve in saiol fluid 1ine control 1ing the flow of fluid 110 said brake, said fluid line extending from said pressure contro1 valve to said brake including a, flow control valve cannected receive fluid under pressum from the out1et of said pressure control valve and a shutole va1ve on said brake, a, pair of fluid lines extending from said. flow contro1 valve 130 the inlet ports of seid shuttle valves, one 0f said lines constituting the normal pressure line and the other an eme1gency pressure line, said flow control valve adapted direct fluid through either the normal 0r emergency pressure line, said lines being so connectecl that one will serve a.s a Vent line for one side o1" the shuttle valve when the other 1ine Conducts fluid under pressum to the other side of said shuttle valve.

11. A hydraulic brake system comprising a, reservoir, a pump 130 deliver fluid under pressure from the reservoir to a fluid line, anti a brake, a pressure contro1 va1ve in said Fluid 1ine controlling the flow of fiuid to said brake, said fluid line extending from said pressure control valve oo said brake including a, flow control valve connected to receive fluid under pressure from the outlet of said pressure control valve and a shuttle valve on said brake, a pair of fiuid lines extending from said flow contro1 valva 120 the in1et ports of said shuttle valves, one of sa.id lines constituting the normal pressure line and the other an emergency pressllre line, said flow control valve adapted to direct; fluid through either the normal 01 emergency pmssure 1ine, said 1ine being connected through the flow control va1ve so that when one 1ine conductg fiuid under pressure 120 one inlet port of the shuttle va1ve, the other line serves as a Vent line from the other port 0f said shuttle valve through the flow control va1ve.

YURGEN Z. VON STACKELBERG. 

